Abstract: Abstract: Objective To evaluate the effect of melatonin on testicular alterations, sperm nuclear integrity and epididymal sperm parameters in rats treated with nicotine. Methods Thirty-two male rats were divided into four groups. Group A received the vehicle, group B received nicotine (1 mg /kg), group C received melatonin (10 mg /kg) and group D received nicotine plus melatonin. Rats were executed 30 days after treatment. The evaluation of spermatogenesis was detected by HE staining. UNEL staining was used to detect the apoptosis of germ cells. The enzyme-linked immunosorbent assay (ELISA) was used for assessment of serum levels of testosterone and luteinizing hormone (LH). WL-9000 sperm quality detection system was used to detect epididymal sperm parameters, and sperm chromatin diffusion test was used to detect sperm chromatin integrity. Results Compared with group A, spermatogenic cell count and Johnsen score were significantly decreased in group B. The number of apoptotic cells increased significantly, and the levels of serum LH and testosterone decreased. The sperm count and motility of epididymis decreased, but the abnormal morphology increased, the proportion of halo sperm decreased significantly, and the DNA fragment index increased significantly (P＜0.05). Compared with group B, the number of spermatogenic cells and Johnsen scores were increased, the number of apoptotic cells decreased, the number and the activity of epididymal sperm increased, but the abnormal morphology decreased in group C and group D. Also the proportion of halo sperm increased and DNA fragment index decreased (P＜0.05). The serum levels of LH and testosterone were higher in group C than those in group B (P＜0.05). There was no significant difference in the serum level of LH between group D and group B. The serum level of testosterone was significantly higher in group D than that of group B (P＜0.05). The DNA fragmentation index was negatively correlated with serum levels of testosterone and LH (r=-0.894, P＜0.001 and r=-0.763, P＜0.001), respectively. There was a positive correlation between DNA fragmentation index and apoptosis of germ cells and abnormal sperm morphology (r=0.782 and 0.837, P＜0.05). Conclusion This study shows that administration of melatonin in nicotine-treated mice increases both quality and quantity of spermatogenesis and integrity of sperm’s chromatin through reducing apoptosis and modifying the testosterone level.

Key words: fertility, nicotine, testis, spermatozoa, spermatogenesis, melatonin